Method for tripping at least one restraining means

ABSTRACT

Proposed is a method for triggering at least one restraint means, triggering signals from peripheral acceleration sensors being released by signals from centrally situated acceleration sensors. In this context, a release threshold is raised in the case of a detected misuse behavior, or the release for the triggering signals is blocked.

BACKGROUND INFORMATION

[0001] The present invention relates to a method for triggering at least one restraint means according to the species defined in the independent claim.

[0002] It is already known to use peripheral acceleration sensors in a vehicle in order to measure accelerations in the vicinity of an impact location during an accident. These are used to then decide whether the restraint means are to be triggered. If there is a triggering signal from such peripheral acceleration sensors (satellites), this triggering signal is tested by a central control unit to determine whether it may be released. A plausibility check follows. For this purpose, the central control unit itself has acceleration sensors for determining this. This is relevant above all for side impact detection.

SUMMARY OF THE INVENTION

[0003] In contrast, the method of the present invention for triggering at least one restraint means having the features of the independent claim has the advantage that a potentially occurring unintentional triggering during driving maneuvers such as driving through potholes or driving over curbs is able to be better suppressed. Therefore, such driving maneuvers should not cause the restraint means to be triggered. In this context, the acceleration sensors in the central control unit are situated such that they detect the acceleration as fast as the peripheral acceleration sensors. If a characteristic as occurs in the case of a pothole or when driving over a curb is detected, a release threshold is raised for a predefined time or the release is blocked for a second predefined time in order to thus suppress unintentional triggering signals for the restraint means. In this instance, the acceleration values as well as the integrated or cumulative accelerations are examined for the plausibility check.

[0004] Advantageous improvements of the method for triggering at least one restraint means, indicated in the independent claim are rendered possible by measures and further refinements specified in the dependent claims.

[0005] It is particularly advantageous that there is a rescue range in order to be able to release the restraint means in the case of an accident even in the case of an increased release threshold or a blocked release. For this purpose, the cumulative transversal accelerations are compared to the rescue band. This is of interest above all in the case of a side impact.

[0006] It is advantageous that the method of the present invention first starts when a noise range for the accelerations is exceeded. Consequently, minimal accelerations resulting from unevenness in a roadway are suppressed.

[0007] Moreover, it is advantageous that an integrator that is realized as software or hardware is used for summing up the accelerations.

[0008] Summing up the acceleration values causes the integration signals to be more harmonic. A filtering occurs in comparison with the acceleration signal. Consequently, statements are able to be made about the total course of a crash, while accelerations only represent an instantaneous survey.

[0009] It is also advantageous that the triggering thresholds in the case of the peripheral acceleration sensors are adjusted as a function of the change in the accelerations. If the acceleration changes significantly in this context as a function of time, the triggering thresholds are significantly lowered in order to cause the restraint means to be triggered in the case of a collision event. In this context, the change in the acceleration is preferably quantized as a function of time in order to thus assign a change in the triggering threshold to an interval of acceleration changes.

[0010] Finally, it is also advantageous that a device for implementing the method of the present invention is provided that has peripheral acceleration sensors and centrally situated sensors, the centrally situated sensors being connected to a control device for triggering the at least one restraint means. The peripheral acceleration sensors are able to be connected to the centrally situated acceleration sensors and the control unit. In this context, the centrally situated acceleration sensors are provided in different sensing directions. This means that there are sensors in the X and the Y direction, the X sensors sensing the acceleration in the travel direction and the Y sensors in the lateral direction, so that a side impact is consequently able to be detected. Alternatively, it is also possible in this context for the centrally situated sensors each to be installed offset from one another at +/−-45° to the travel direction axis.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Exemplary embodiments of the present invention are shown in the drawings and are explained in detail in the following description. FIG. 1 shows a configuration of acceleration sensors in the vehicle; FIG. 2 shows centrally situated acceleration sensors in the vehicle that are positioned in different sensing directions; FIG. 3 shows a diagram for representing the method of the present invention; FIG. 4 shows a second diagram for representing the method of the present invention; FIG. 5 shows a third diagram for representing the method of the present invention; FIG. 6 shows a diagram for illustrating the change in the triggering threshold as a function of acceleration changes; and FIG. 7 shows a flow chart of the method of the present invention.

SPECIFICATION

[0012] Restraint means such as airbags and belt tighteners are increasingly used in greater numbers in motor vehicles. In this context, the unintentional triggering of airbags is an important objective for preventing injuries to the vehicle occupants. In the case of driving maneuvers such as driving over a curb or through a pothole, there are so-called misuses in which case it is not necessary to trigger the restraint means. Therefore, the triggering if even requested by a satellite should be suppressed in such a case.

[0013] Therefore in accordance with the present invention, a method for triggering at least one restraint means is used that detects such misuses using centrally situated acceleration sensors and suppresses a triggering signal from peripheral acceleration sensors for a predefined time provided that the signals from the centrally situated acceleration sensors do not exceed a predefined rescue band or existing release threshold. Accelerations in the lateral directions of the vehicle as well as cumulative accelerations in the travel and lateral direction of the vehicle are examined for this purpose.

[0014] A configuration of acceleration sensors in a vehicle is represented in FIG. 1. Vehicle 1 has a central control unit 2 in the vehicle that is situated at the vehicle tunnel, for example. As shown in FIG. 2, central control unit 2 has acceleration sensors 8 and 11, which are each situated in the X and Y direction, 0°/90° concepts and +/−45° concepts being usable. 0° corresponds to the x axis and 90° to the y axis.

[0015] Acceleration sensor 8 is connected to electronics 9, which amplifies and digitalizes the acceleration signal, so that a microcontroller 10 as a processor to which one data output of electronics 9 is connected is able to process the acceleration signal from acceleration sensor 8. An electronics 12, which processes the signals from acceleration sensor 11 in the same manner, is connected to a second data input of microcontroller 10. The amplification of electronics 9 or 12 may alternatively also be assigned to acceleration sensors 8 and 11, so that an acceleration sensor and a measured value amplifier are on a chip. The analog-digital conversion may be assigned to microcontroller 10, which then has analog inputs to which the acceleration sensors are connected.

[0016] Central control unit 2 is connected via a first data input/output to a peripheral acceleration sensor 3, via a second data input/output to a peripheral acceleration sensor 4, via a third data input/output to a peripheral acceleration sensor 5, via a fourth data input/output to a peripheral acceleration sensor 6, and via a fifth data input/output to a peripheral acceleration sensor 7. These connections may alternatively also be made via a bus, a sensor bus, or a triggering bus.

[0017] Peripheral acceleration sensors 3, 4, 5, 6, and 7 each have an own control device, so that if need be triggering signals are transmitted to central microcontroller 10. Alternatively, it is also possible for peripherally situated acceleration sensors 3 through 7 to have an electronics that solely amplifies and digitalizes the acceleration signals and for the acceleration signals to be centrally processed in microcontroller 10. A mixed assembly with components of both concepts is also possible here. Peripheral acceleration sensors 3 through 7 are positioned for sensing side impact as well as for sensing front impact. In this context, peripheral acceleration sensor 5 is provided for the front impact sensing. It is possible for additional sensors to be housed in different parts of the vehicle and to be connectable to central control unit 2. It is also possible to use less acceleration sensors than shown here.

[0018] Shown in FIG. 3 is an acceleration-time diagram that displays an acceleration signal 18 from acceleration sensor 8, which measures the acceleration in the Y direction, e.g. the lateral direction of vehicle 1, as a function of time. Therefore, the ordinate of the diagram is marked by a_(y) and the abscissa by t.

[0019] This acceleration signal 18 is compared here to different thresholds 13, 14, 15, and 16. If acceleration signal 18 exceeds threshold 13 for the first time, the method and the present invention begins and continues to be carried out even when threshold 13 is no longer being exceeded. Therefore, threshold 13 represents the noise band. Thresholds 13, 14, 15, and 16 shown here are symmetrical about the abscissa in order to measure accelerations in both directions, i.e. +Y and −Y, +Y accelerations meaning from the right and −Y accelerations meaning from the left in this instance.

[0020] Threshold 16 initially represents the release threshold. If a satellite 3-7 transmits a triggering signal, microcontroller 10 checks whether acceleration signal 18 is above threshold 16. If that is the case, the restraint means are released to be activated. If that is not the case, the restraint means are not released to be activated.

[0021] If threshold 14 is exceeded by the acceleration signal, but threshold 15 is not exceeded, an acceleration indicating a misuse, i.e. driving through a pothole or over a curb, is detected. Therefore, it is necessary in some instances to suppress the triggering signal. The release threshold is therefore increased from threshold value 16 to threshold value 15 for a time 17. The algorithm thereby becomes less sensitive.

[0022] Thresholds 13 and 16 are at several G (gravitational acceleration), while thresholds 14 and 15 are well over 10 G. In response to an acceleration signal between thresholds 14 and 15, the release threshold for centrally situated Y sensor 8 is raised to value 15 for predefined time 17. Consequently, the triggering algorithm described here becomes less sensitive. If during time 17 the release threshold at value 15 is exceeded by the acceleration signal, and satellite 3-7 still transmits a triggering signal, the restraint means are released for activation.

[0023] Release threshold 16 is raised to value 15 for predefined time 17, which is determined from experimental data. This experimental data is laid out such that driving over a curb or through a pothole, for example, is measured over time, so that the method of the present invention is available again as quickly as possible for detecting an impact in order to provide optimum protection for the vehicle occupants. The underlying triggering algorithm that is run in control unit 2 on processor 10 may be refined in that threshold 16 is only raised when acceleration signal 18 shows a maximum in the acceleration range between thresholds 14 and 15 and does not pass through this interval to increase further. When acceleration signal 18 exceeds release threshold 15, a triggering signal from peripheral acceleration sensors is released. In this case, there is an impact at high speeds.

[0024] It is provided in a further refinement for the cumulative acceleration signal of Y acceleration sensor 8 to also be compared to a fixed rescue band that is a threshold value that is symmetrical to the time axis. When this rescue band is exceeded by the cumulative acceleration signal, a so-called side impact exists, and a triggering signal from peripheral acceleration sensor 3-7 is released. This is particularly the case when the acceleration signal is still under threshold 14.

[0025] Shown in FIG. 4 is a cumulative acceleration signal time diagram in which cumulative acceleration signal 19 dv_(y) in the Y direction, i.e. in the transverse direction of the vehicle, is checked as a function of time for a zero crossing and consequently for a sign change. The zero crossing is viewed here as the threshold value, namely the time axis, being exceeded.

[0026] The ordinate indicates the cumulative acceleration signal in the Y direction, while the abscissa indicates the time. Therefore, the ordinate is designated by dv_(y) and the abscissa by t. If accelerations are summed up, there is a speed signal, the acceleration being integrated in particular in this instance.

[0027] If the zero crossing of the cumulative acceleration signal is detected, as soon as the triggering request (triggering signal) of the satellite occurs within predefined time 38, a release for the triggering signal is blocked for a predefined time 21. Cumulative acceleration signal 19 of central acceleration sensor 8, of the Y acceleration sensor in this instance, must have a sign change after a predefined time after the start of the algorithm or of the method of the present invention, so that blocking is able to occur. Time 37, which signal 19 needs to experience a zero crossing and consequently a sign change, must therefore be less than predefined time 38. This prevents the cumulative acceleration signal from not being observed for a long measuring time with respect to the zero crossing for the blocking.

[0028] A rescue band 39 is then symmetrically situated and cumulative acceleration signal 19 must exceed this threshold 39 to generate a release signal for a triggering signal from a peripheral acceleration sensor. This rescue band 39 is present to permit the detection of a side impact despite the detected misuse.

[0029] Shown in FIG. 5 is a further diagram that represents cumulative accelerations dv_(x) as a function of time. In this instance, the acceleration signal from X acceleration sensor 11 is integrated (signal 22) and compared to a fixed threshold value 20. As soon as this value 20 is reached, the blocking is carried out for predefined time 21. This blocking is only able to be overridden by signal 19 from the Y sensor when rescue band 39 is exceeded.

[0030]FIG. 6 shows how triggering threshold 24 is changed as a function of changes in acceleration signal 25 of a peripheral acceleration sensor. The diagram in FIG. 6 shows an acceleration-time diagram, acceleration signal 25 changing its slope. Acceleration a is marked off on the ordinate while time t is on the abscissa. If the slope changes significantly, threshold 24 is lowered for a predefined time to then return to a neutral value. If acceleration signal 25 again shows a significant change, triggering threshold 24 is raised as a function of this change. Therefore, threshold 24 is increased as a function of the change in acceleration signal 25. In this context, the changes in acceleration are divided into intervals and a threshold change is assigned to each of these intervals. Consequently, a quantization exists.

[0031]FIG. 7 shows a flowchart of the method according to the present invention. In method step 26, the peripheral acceleration sensors detect that restraint means are to be triggered since acceleration signals 25 have exceeded a triggering threshold 24. These triggering signals are transmitted to a central control unit 2. In method step 27, central control unit 2 checks on the basis of its own acceleration signals acquired by centrally situated acceleration sensors 8 and 11 whether these triggering signals may be released. In method step 28, this is checked as shown above on the basis of release threshold 16 or 15 or on the basis of an existing blocking of the triggering signal. In this context, a check is also made to determine whether rescue band 39 is being exceeded.

[0032] If the signals may be released, the restraint means are triggered in method step 29. If this is not the case, release thresholds 16 are raised for a predefined time in method step 30 or the triggering signal is blocked. Method step 31 checks whether raised release threshold 15 or rescue band 39 is being exceeded. If that is the case, the triggering of the appropriate restraint means is released in method step 29, and if this is not the case, the method ends in method step 32.

[0033] The method of the present invention always starts as soon as peripheral acceleration sensors 3-7 detect a side impact. However, it may also be used for other types of impact. 

What is claimed is:
 1. A method for triggering at least one restraint means, a triggering signal from a peripheral acceleration sensor (3-7) situated in a vehicle being released for the at least one restraint means by signals from an acceleration sensor (8, 11) centrally positioned in the vehicle (1) to trigger the at least one restraint means, wherein when the signals exceed a threshold value (14, 20), a release threshold (16) for the signals is raised for a first predefined time (17) or the release for the triggering signal is blocked for a second predefined time (21).
 2. The method as recited in claim 1, wherein accelerations or cumulative accelerations are used as the signals.
 3. The method as recited in claim 1 or 2, wherein when the cumulative accelerations (19) pass through a sign change due to a zero crossing, or when the cumulative accelerations (22) reach a threshold value (20), the release is blocked for the predefined time (21).
 4. The method as recited in one of the preceding claims, wherein when the cumulative transversal accelerations measured by the centrally positioned acceleration sensor (8, 11) exceed a rescue range (39) in the vehicle, the triggering signal is always released.
 5. The method as recited in claim 1, 2, 3, or 4, wherein a triggering threshold (24) is set for the at least one peripheral acceleration sensor (3-7) as a function of the acceleration change.
 6. The method as recited in one of the preceding claims, wherein a noise range about the acceleration is taken into consideration, only accelerations greater than the noise band at the start of the method being taken into consideration.
 7. The method as recited in one of the preceding claims, wherein an integrator is used in each case for summing up the accelerations.
 8. The method as recited in one of the preceding claims, wherein the accelerations are determined in different sensing directions.
 9. A device for implementing the method as recited in one of claims 1 through 8, wherein the device, which is present in a vehicle (1), has at least one peripheral acceleration sensor (3-7) and centrally situated acceleration sensors (8, 11), the centrally situated acceleration sensors (8, 11) being able to be connected to a processor (10) for triggering the at least one restraint means, and the at least one peripheral acceleration sensor (3-7) being able to be connected to the centrally positioned acceleration sensors (8, 11).
 10. The device as recited in claim 9, wherein the centrally positioned acceleration sensors (8, 11) are present in different sensing directions. 